U.S. Pat. No. 5,141,517 to Shutt discloses a retractable instrument having a locking mechanism which can be automatically actuated for selective positioning and locking of the instrument. The handle of the instrument includes several abutment elements which cooperatively engage with corresponding transverse bends in the end of an instrument support shaft within the handle. A slidable actuating pin moves the support shaft axially so that the support shall engages positively with one of the abutment elements, thereby locking the support shaft and preventing rearward axial motion of the instrument after it is locked in place.
U.S. Pat. No. 4,674,500 to DeSatnick discloses a sheathed knife instrument having a blade which is selectively movable by way of a sliding element on the handle. The sliding element is controlled by finger movement, thereby permitting single-handed operation of the knife instrument. The sliding element moves axially and can be rotated transverse to that axis to lock the knife blade in place.
Neither of the devices permits effective single-handed retractable operation of a surgical instrument, such as a surgical knife, with simple, bi-directional control.
It is therefore an object of the present invention to provide a tool support assembly having bi-direction position control and being operable with one hand.
It is an other object of the present invention to provide a surgical instrument having bi-directional instrument position control and means for selectively locking the surgical instrument in any number of positions with one hand.